Podcast
Questions and Answers
What is the primary function of a consensus protocol in state machine replication?
What is the primary function of a consensus protocol in state machine replication?
- To ensure the atomic broadcast of input messages. (correct)
- To limit the number of nodes in a distributed system.
- To initiate the recovery process of failed nodes.
- To verify the output responses of the state machines.
Which statement best describes the relationship between state machines and nodes in a replicated environment?
Which statement best describes the relationship between state machines and nodes in a replicated environment?
- Each node operates independently without synchronization.
- State machines are irrelevant to the functioning of nodes in replication.
- Nodes can evolve their states individually, but must do so in exactly the same manner. (correct)
- All nodes must replicate the state machine's initial conditions.
What advantage does state machine replication provide when a node fails?
What advantage does state machine replication provide when a node fails?
- It allows remaining nodes to recover the state or data of the failed node. (correct)
- It prevents any changes from being made until the node is recovered.
- It guarantees that all nodes will shut down safely.
- It reduces the workload on the remaining nodes.
Which of the following is NOT a characteristic of deterministic state machines in the context of state machine replication?
Which of the following is NOT a characteristic of deterministic state machines in the context of state machine replication?
In the context of state machine replication, a successful consensus indicates what among the nodes?
In the context of state machine replication, a successful consensus indicates what among the nodes?
What is the primary purpose of consensus algorithms in distributed systems?
What is the primary purpose of consensus algorithms in distributed systems?
Which of the following describes a byzantine fault in distributed systems?
Which of the following describes a byzantine fault in distributed systems?
What is a significant challenge posed by byzantine nodes in P2P networks?
What is a significant challenge posed by byzantine nodes in P2P networks?
In a deterministic finite automata, what does the transition function δ model?
In a deterministic finite automata, what does the transition function δ model?
What is the result of successful database replication in terms of system resilience?
What is the result of successful database replication in terms of system resilience?
Which of the following statements accurately describes atomic broadcast in distributed computing?
Which of the following statements accurately describes atomic broadcast in distributed computing?
What distinguishes non-malicious byzantine faults from malicious ones?
What distinguishes non-malicious byzantine faults from malicious ones?
Which component is NOT part of the 5-tuple defining a deterministic finite automata?
Which component is NOT part of the 5-tuple defining a deterministic finite automata?
In a partially/eventually synchronous network, what assumption is made about the network's behavior over time?
In a partially/eventually synchronous network, what assumption is made about the network's behavior over time?
Which of the following statements is true regarding faulty nodes in a distributed system?
Which of the following statements is true regarding faulty nodes in a distributed system?
What describes the crash failure model in a distributed system?
What describes the crash failure model in a distributed system?
In the Byzantine Generals Problem, what is the role of loyal generals?
In the Byzantine Generals Problem, what is the role of loyal generals?
What determines whether an action taken by generals is considered a good decision in the Byzantine fault model?
What determines whether an action taken by generals is considered a good decision in the Byzantine fault model?
Which of the following scenarios exemplifies a byzantine fault?
Which of the following scenarios exemplifies a byzantine fault?
What is a key characteristic of the traitorous generals in the Byzantine model?
What is a key characteristic of the traitorous generals in the Byzantine model?
In the context of fault models, what distinguishes byzantine failures from crash failures?
In the context of fault models, what distinguishes byzantine failures from crash failures?
Flashcards
Partially/Eventually Synchronous Network
Partially/Eventually Synchronous Network
A network that eventually behaves as a synchronous network, even though it might be asynchronous for some time.
Faulty Node
Faulty Node
A node (process) in a distributed system that behaves differently than expected, potentially due to intentional or unintentional issues.
Crash Failure
Crash Failure
A type of fault where a node simply stops responding without any prior warning due to hardware/software failure.
Byzantine Failure
Byzantine Failure
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Honest/Correct Node
Honest/Correct Node
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Byzantine Generals Problem
Byzantine Generals Problem
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Loyal General
Loyal General
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Traitor General
Traitor General
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State Machine Replication (SMR)
State Machine Replication (SMR)
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Atomic Broadcast
Atomic Broadcast
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Distributed Consensus
Distributed Consensus
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Consensus Protocol
Consensus Protocol
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Deterministic State Machine
Deterministic State Machine
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Byzantine Fault
Byzantine Fault
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Consensus Algorithm
Consensus Algorithm
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Database Replication
Database Replication
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State Machine
State Machine
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P2P Networks
P2P Networks
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Deterministic Finite Automata (DFA)
Deterministic Finite Automata (DFA)
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Fault-Tolerant Computing
Fault-Tolerant Computing
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Study Notes
Course Information
- Course title: CSE446: Blockchain & Cryptocurrencies
- Lecture: 4 - Distributed Systems & Consensus Algorithms
Distributed System Model
- A distributed system comprises multiple computers (nodes)
- Nodes are geographically dispersed but interconnected via a communication network
- Each node is autonomous, operating independently
- Nodes communicate using the network
Distributed System Model (detailed)
- Each node has:
- A processor
- Communication network
- Software
- Non-volatile storage
- Each processor has volatile memory inaccessible by other nodes
- Each node has a network interface card (NIC) for network connection
- Software primarily consists of the operating system (OS)
- Non-volatile storage stores programs and data
Distributed System Model (alternative view)
- Distribution can be viewed as a logical construct from an application standpoint
- Distributed applications consist of concurrently executing processes
- Executing processes involves sequential programs
- Concurrent processes can execute on a single processor or use a multi-programming approach
- Primary focus is on parallel processes running across different nodes
Distributed System Model - Types of Concurrent Processes
- Independent: Processes with disjoint sets of accessed objects
- Competing: Processes sharing resources but not exchanging information
- Cooperating: Processes exchanging information via shared data objects or message passing
Distributed System Model - Network Types
- P2P (Peer-to-Peer) and client/server networks
- Synchronous, asynchronous, partially/eventually synchronous
- Synchronous network messages have bounded latency of T + ∆
- Asynchronous network requires message to be eventually delivered but latency not bounded
- Partially/eventually synchronous assumes eventual synchronous behavior despite periods of asynchrony
Fault Model
- Different behaviors of nodes (processes) for reasons like errors and corruption (faulty nodes)
- Up to f nodes (out of N total) may experience failures(N/2 or N/3)
- Crash failure: Nodes temporarily fail to respond due to hardware/software without prior warning
- Byzantine failure: More malicious and complex fault. Nodes send inconsistent or misleading information
- Byzantine fault is generally due to a malicious actor or software bug or compromised machines
Fault Model: Byzantine Fault
- Two types of nodes: loyal or traitors
- Loyal nodes must agree on a plan of action
- The number of malicious nodes (traitors) should be limited such that loyal nodes can still successfully arrive at a correct decision.
- General 2 and General 3 received conflicting messages about the decision.
Need for Consensus Algorithm
- Consensus is crucial in distributed applications, particularly database replication
- Database replication involves storing data in multiple sites/nodes
- Replication enhances resilience against node failures, improving data availability
- Copying data from one server to another ensures that users share the same data avoids inconsistencies
State Machine
- An abstract model of a digital computer
- Has a defined set of states
- Contains rules for transitioning between states triggered by input symbols
- Can be deterministic or non-deterministic
Atomic Broadcast
- In fault-tolerant systems, atomic broadcast ensures all nodes receive messages in the same order
State Machine Replication (SMR)
- Replication approach that mirrors the state changes of a machine across several nodes
- The state machine takes messages, performs calculations, then sends responses.
- Machines can be replicated and work individually
- Machines work together when one fails
State Machine Replication (protocol)
- A protocol for distributed systems is necessary for atomic broadcast of messages
- This ensures that all nodes are updated simultaneously and in the same order
- The protocol is called a consensus protocol. This enables a shared state across all nodes.
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Description
Explore the fundamental concepts of distributed systems and consensus algorithms in this quiz. Understand the architecture of nodes, their components, and how they communicate within a network. Delve into both physical and logical views of distributed systems as you test your knowledge.
